The present invention relates to an apparatus and a method for assembling an optical cable. In the optical cable, a grooved spacer has an elongated plastic rod with a plurality of spiral grooves in its circumferential surface and optical fiber ribbons are held within the respective spiral grooves of the spacer.
Optical cables, in which a grooved spacer has an elongated plastic rod with a plurality of spiral grooves in its circumferential surface and optical fiber ribbons are held within the respective spiral grooves, are now widely employed as a representative example of the optical cable shown in FIG. 9.
FIG. 9(A) is a perspective view of a spacer, FIG. 9(B) is a transverse sectional view of an optical fiber ribbon, and FIG. 9(C) is a transverse sectional view of an optical cable.
As shown in FIG. 9, an optical cable comprises a spacer 30, an anti-tension element 31, a plastic molded element 32, a plurality of spiral grooves 33, optical fiber ribbons 34, wires 34a, a wire covering 34b, an upper winding tape 35, a cable core 36, and an outer covering 37.
In this optical cable, the spacer 30 is formed from the plastic molded element 32 and the anti-tension element 31.
The anti-tension element 31 is formed of a steel wire, a twisted wire, FRP or the like. The plastic molded element 32 is made of polyethylene or the like, and has a single or a plurality of spiral grooves 33 in the periphery of the anti-tension element 31. In this case, the outer diameter of the spacer ranges from about 5 mm to 30 mm. A plurality of wires 34a is formed by covering glass fiber of quartz or the like with ultraviolet curing resin or the like. The optical fiber ribbons 34 are formed by disposing the plurality of wires 34a in parallel and then covering all the wires 34a with the wire covering 34b made of ultraviolet curing or the like.
The optical fiber ribbons 34 are laminated and held within the spiral groove 33 of the spacer 30, and the upper winding tape 35 is applied to the outer periphery of the plastic molded element 32 to make the cable core 36. Then the plastic or metal outer covering 37 is applied to the perimeter of the cable core 36 to complete the optical cable. Although there has been shown an exemplary optical cable in which the laminated optical fiber ribbons 34 are respectively held within the spiral grooves 33 of the spacer 30 in FIG. 9, a single optical fiber ribbon having one wire 34a may be used. Further, the optical fiber ribbons held within the spiral grooves 33 may be formed by twisting a plurality of single wires and then press-winding the single wires. Moreover, the spiral direction of the spiral groove of the spacer may be set to the opposite direction to that shown in FIG. 9(A).
In the case of such the optical cable as mentioned above, a step of holding the optical fiber ribbons within the spiral grooves of the spacer to manufacture cable cores is called a cable assembly step. The cable assembly step is carried out by an optical cable assembly apparatus. FIG. 10 is an elevational view of a main part of an optical cable assembly apparatus. The optical cable assembly apparatus comprises a supply reel 41, supplying a spacer 42, a dancer roller 43, brake rollers 44, a guide roller 45, a brake mechanism 46, a spacer paying-out portion 47, a stationary ribbon supply unit 48, supply reels 49 supplying optical fiber ribbons 50, a gathering die 51, a gathering portion 53 winding an upper winding tape 52 onto the spacer 42 to make a cable core 54, a guide roller 55, capstan rollers 56, a dancer roller 57, a take-up mechanism 58, a taking-up reel 59, and a taking-up portion 60. In FIG. 10, X-X is a line axis around which the spacer paying-out portion 47 and the taking-up portion 60 revolve.
A main part of the optical cable assembly apparatus includes the spacer paying-out portion 47, the stationary ribbon supply unit 48, the gathering portion 53 and the taking-up portion 60. The spacer paying-out portion 47 comprises the supply reel 41 and the brake mechanism 46. The supply reel 41 revolves around the line axis X-X in the direction of the spiral groove of the spacer 42. The number of revolutions thereof is in synchronization with the number of rotations of the spiral groove thereof. The brake mechanism 46 comprises the dancer roller 43, the brake rollers 44 and the guide roller 45. The brake mechanism 46 is used to apply back tension to the spacer 42 sent out of the supply reel 41. That is, the spacer 42 sent out of the supply reel 41 is wound on the brake rollers 44 via the dancer roller 43, so that the back tension is applied to the spacer 42. The diameters of the dancer roller 43 and the brake roller 44 ranges from 600 to 800 mm, and the diameter of the guide roller 45 ranges from about 100 to 600 mm.
The spacer 42 applied back tension is sent out of the spacer paying-out portion 47 via the guide roller 45 toward the gathering portion 53. The difference between speed in extending the spacer 42 from the supply reel 41 and speed in transferring the spacer 42 on the brake roller 44 is temporarily adjusted by displacing the position of the dancer roller 43. The guide roller 45 is used to make a direction of letting out the spacer 42 from the brake rollers 44 coincide with the direction of the line axis X-X.
The spacer 42 sent out of the spacer paying-out portion 47 runs forward along the line axis X-X while rotating on its center axis. However, as the rotation on its center axis coincides with the rotation of the spiral groove, the spiral groove spatially appears stationary even though it runs forward. Accordingly, the spiral groove of the spacer 42 always stays at the same position in the circumferential direction.
On the other hand, the optical fiber ribbons 50 are sent out of a plurality of supply reels 49 and then guided to the spiral groove of the spacer 42. The plurality of supply reels 49 are installed in the stationary ribbon supply unit 48 fixed to the ground. The optical fiber ribbons 50 and the spacer 42 are gathered at the gathering die 51, and then the upper winding tape 52 is wound thereon in the gathering portion 53. Since the spiral groove of the spacer 42 stays at the same position in the circumferential direction at the place of the gathering die 51 of the gathering portion 53, the optical fiber ribbons 50 can be held within the spiral groove by only guiding the optical fiber ribbons 50 to the same position. Next, the upper winding tape 52 is wound on the spacer 42 in the gathering portion 53 after the optical fiber ribbons 50 are held within the spiral groove, so that the cable core 54 is completed. In this case, it may be arranged to hold the spacer 42 with a coarse winding element or the like instead of winding the spacer 42 with the upper winding tape 52.
The cable core 54 completed in the gathering portion 53 runs forward to the taking-up portion 60. The taking-up portion 60 comprises the take-up mechanism 58 and the taking-up reel 59, and revolves around the line axis X-X in synchronization with the revolution of the spacer paying-out portion 47. The take-up mechanism 58 is used to add a take-up force to the cable core 54. The take-up mechanism 58 comprises the guide roller 55, the capstan rollers 56 and the dancer roller 57. The cable core 54 that has entered the take-up mechanism 58 of the taking-up portion 60 along the line axis X-X is wound on the capstan rollers 56 via the guide roller 55.
Then the cable core 54 is wound on the taking-up reel 59 via the dancer roller 57. In this case, the guide roller 55 is used to guide the cable core 54 to the capstan rollers 56. The capstan rollers 56 is used to add the take-up force to the cable core 54. The dancer roller 57 is used to temporarily adjust the difference between speed in taking up the cable core 54 on the capstan rollers 56 and speed in winding the cable core 54 on the taking-up reel 59.
Since the spacer is the plastic molded element having the high rigid anti-tension element in its central part and quite a thick rod body having a diameter of 5 mm-30 mm, it has substantially great bending rigidity. Consequently, the spacer wound on the supply reel has an extremely strong winding habit. When it is attempted to bend a longitudinally part of the spacer in a direction opposite to a winding direction of the spacer wound on the supply reel, a bending force is generated which is directed in a direction against the winding habit, and then rotational force on the center axis is caused to that part of the spacer thereby. Accordingly, the spacer rotates on the center axis, and then twisting is generated thereto.
As the twisting of the spacer is generated between the roller used to give bending in the opposite direction to the winding direction and another roller in front of or behind it, the spacer between them undergoes variation in the spiral pitch of the spiral groove. Further, the cable core also has a strong winding habit because the optical fiber ribbons, which is held within the spiral groove of the spacer to make the cable core, have substantially no effect on the bending rigidity of the spacer. Accordingly, the twisting is generated to the cable core as in the case when the spacer is bent in the direction against the winding habit of the cable core.
On the other hand, the dancer roller 43 and the brake roller 44 in the spacer paying-out portion 47, and the capstan rollers 56, the dancer roller 57 and the taking-up reel 59 in the taking-up portion 60, as shown in the elevational view of FIG. 10, are rotated clockwise like the supply reel 41 in order to extend and wind the spacer 42 or to take up and wind the cable core 54. On the contrary, the guide roller 45 in the spacer paying-out portion 47 and the guide roller 55 in the taking-up portion 60 are rotated counterclockwise in order to guide the spacer 42 or the cable core 54 thereto.
As a result, the spacer 42 in the portions of the guide rollers 45 and 55 is subjected to bending in the direction against the winding habit and the twisting on the center axis is caused to the spacer 42 or the cable core 54 by the opposite rotations of the guide rollers 45 and 55. As this twisting of the spacer 42 or the cable core 54 substantially affects the gathering portion 53, the spiral pitch of the spiral groove of the spacer 42 or the cable core 54 in front of and behind the gathering portion 53 deviates from a normal value, that is, becomes greater or smaller than the normal value. Accordingly, when the optical fiber ribbons are held within the spiral groove of the spacer, the optical fiber ribbons are to be held in such a state that the spiral pitch of the spacer has deviated from the normal value.
As the optical fiber ribbons and the spacer are gathered in such a state that they have been given an allowance for predetermined expansion and contraction according to a design thereof, a predetermined back tension is applied to them at a point of time they pass through the gathering portion. This back tension is released at the time the cable core has been wound on the taking-up reel. In this case, the back tension is determined so that the optical fiber ribbons may be held within the spiral groove in a manner that they give an allowance for predetermined expansion and contraction with respect to the spacer.
The optical fiber ribbons held within the spiral groove of the spacer have the stranding ratio which obtained from the distance between the position of the optical fiber ribbons and the center axis of the spacer, and the spiral pitch. The optical fiber ribbons are set longer than the spacer by a length equivalent to the stranding ratio. Accordingly, if the spiral pitch of the spiral groove varies, the length of the optical fiber ribbons held in the spiral groove also varies.
If the spacer passes through the gathering portion with the spiral pitch fluctuated due to the twisting and then the optical fiber ribbons are held within the spiral groove, the length of the optical fiber ribbons held therein deviates from the normal value by the length equivalent to the fluctuation of the spiral pitch. Further, if the cable core is wound on the taking-up reel in the state above-mentioned and then the spiral pitch is returned to the original state since the cable core is released from the twisting at the taking-up portion, the deviation of the expansion and contraction of the optical fiber ribbons from the normal value becomes apparent due to fluctuations in the length of the optical fiber ribbons. If the expansion and contraction of the optical fiber ribbons greatly deviate from the normal value, the aging of the optical fiber ribbons will be shortened, the transmission loss of the optical fiber ribbons will be increased, and therefore the quality of the cable cores and the optical cables manufactured therefrom will be deteriorated.
As set forth above, if the spacer or the cable core is passed through the rollers that provide bending in the direction against the winding habit, it undergoes the twisting. Further, if the twisting affects the gathering portion, the quality of optical cables will be deteriorated.
Accordingly, an object of the present invention is to provide an apparatus and a method for assembling an optical cable, wherein it is possible to prevent the twisting of a spacer or a cable core in a gathering portion which results from the winding habit of the spacer during assembling cables.
The above-mentioned object can be achieved by an apparatus for assembling an optical cable along a line axis comprising:
a spacer paying-out portion, having a supply reel on which a grooved spacer having an elongated plastic rod with a plurality of spiral grooves in its circumferential surface is wound, rotational direction for paying-out the spacer therefrom while revolving around a line axis;
a stationary supply unit for supplying a plurality of optical fiber ribbons to be inserted into respective spiral grooves of the spacer;
a gathering portion for inserting and holding the optical fiber ribbons in the respective spiral grooves of the spacer running forward and rotating on its center axis to form a cable core;
a taking-up portion, having a taking-up reel on which the cable core is, for winding the cable core on the taking-up reel while revolving around the line axis;
a first winding roller rotating in a rotational direction identical to the rotational direction of the supply reel of the spacer, for winding the spacer, the first winding roller being disposed substantially and adjacently before the gathering portion in a spacer conveying direction; and
a second winding roller rotating in a rotational direction identical to the rotational direction of the supply reel of the spacer, for winding the cable core, the second winding roller being disposed substantially and adjacently after the gathering portion in the spacer conveying direction, wherein the first and second winding rollers are revolved around the line axis in synchronization with the revolution of the spacer paying-out portion.
In the above-mentioned construction, the first or second winding roller is installed adjacently before and after the gathering portion, that is, installed between the gathering portion and places where the spacer is wound on any one of the first and second rollers in the front of or behind the gathering portion.
It is preferable that the first and second winding rollers are respectively installed in the spacer paying-out portion or the taking-up portion.
It is also preferable that the first or second winding roller may be installed between the spacer paying-out portion or the taking-up portion and the gathering portion. With this installation of the first and second winding rollers, the spacer is not given bending in a direction against the winding habit of the spacer in front of and behind the vicinity of the gathering portion. Accordingly, it is possible to prevent the twisting of the spacer and to stabilize the length of optical fiber ribbons to be held within the spiral groove of the spacer. As a result, it is possible to prevent the transmission characteristics of the optical fiber ribbons from being deteriorated.
Further, provision of the first or second winding roller in the spacer paying-out portion or the taking-up portion makes it possible to use the facilities for revolving the winding roller in common with those for revolving the spacer paying-out portion or the taking-up portion, thus resulting in reducing the facility cost.
Further, In the above-mentioned construction, it is preferable that each of the first and second winding roller comprises a rotary roller with a roller surface on which one of the spacer and the cable core is wound, the rotary roller having a side roller for pushing the one along the roller surface in parallel with an rotational direction of the rotary roller.
It is also preferable that each of the first and second winding rollers comprises a rotary roller with a fleeting ring which is rotatably fitted onto a roller surface of the rotary roller.
The use of the rotary roller with the side roller as the winding roller or the rotary roller with the fleeting roller can suppress centrifugal force resulting from the revolution around the line axis in comparison with the use of the winding roller using the combination of plurality of rollers, and make it possible to reduce the facility cost due to the use of only one rotary. Moreover, the outgoing wire direction can be stabilized by preventing the incoming and outgoing wire directions of the spacer from being same direction on top of each other. Further, provision of the fleeting ring as the winding roller makes it possible to prevent from giving damage to the spacer because the fleeting ring pushes the spacer with the surface thereof. Moreover, the winding roller may comprise more than one roller and wherein the spacer or the cable core is stretched across and wound on the rollers.
The above-mentioned object can be also achieved by an apparatus for assembling an optical cable along a line axis, the apparatus comprising:
a spacer paying-out portion, having a supply reel on which a grooved spacer having an elongated plastic rod with a plurality of spiral grooves in its circumferential surface is wound, for paying-out the spacer therefrom while revolving around a line axis;
a stationary supply unit for supplying a plurality of optical fiber ribbons to be inserted into respective spiral grooves of the spacer;
a gathering portion for inserting and holding the optical fiber ribbons in the respective spiral grooves of the spacer running forward and rotating on its center axis to form a cable core;
a taking-up portion, having a taking-up reel on which the cable core is, for winding the cable core on the taking-up reel while revolving around the line axis;
a first winding roller rotating in a rotational direction identical to the rotational direction of the supply reel of the spacer, for winding the spacer, the first winding roller being disposed in the spacer paying-out portion; and
a second winding roller rotating in a rotational direction identical to the rotational direction of the supply reel of the spacer, for winding the cable core, the second winding roller being disposed in the taking-up portion,
wherein both the first and second winding rollers are rotated in a rotational direction which is coincided with the rotational direction of the supply reel.
For instance, a dancer roller or a capstan roller can serve as the winding roller without installing the winding roller by changing the outgoing wire position of the dancer roller or the incoming wire position of the capstan roller, so that the facility cost also becomes reducible.
Moreover, the above-mentioned object can be attained by a method for assembling an optical cable along a line axis, the method comprising steps of:
(a) supplying a grooved spacer having an elongated plastic rod with a plurality of spiral grooves on its circumferential surface from a supply reel rotating in a rotational direction while rotating the spacer about its center axis, the supply reel being disposed in a spacer paying-out portion which revolves around the line axis;
(b) supplying optical fiber ribbons from a stationary ribbon supply unit;
(c) winding the spacer on a winding roller rotating in a rotational direction identical to the rotational direction of the supply reel while revolving around the line axis in synchronization with the revolution of the spacer paying-out portion;
(d) guiding the optical fiber ribbons into the spiral grooves respectively and then holding the optical fiber ribbons within the spiral grooves respectively so as to form a cable core in a gathering portion;
(e) winding the cable core on a winding roller rotating in an rotational direction identical to the rotational direction of the supply reel and revolving around the line axis in synchronization with the revolution of the spacer paying-out portion; and
(f) winding the cable core on a taking-up reel in a taking-up portion while revolving around the line axis in synchronization with the revolution of the spacer paying-out portion.
In the above-mentioned method, it is advantageous that the method further comprising the steps of:
making a direction of the spacer coincide with the line axis before the step (c); and
making a direction of the cable core coincide with the line axis before the step (e).
With this above-mentioned method, the spacer is not given bending in a direction against the winding habit of the spacer in front of and behind the vicinity of the gathering portion. Accordingly, it is possible to prevent the twisting of the spacer and to stabilize the length of optical fiber ribbons to be held within the spiral groove of the spacer. As a result, it is possible to prevent the transmission characteristics of the optical fiber ribbons from being deteriorated.
Other objects, features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.